Photochromic material and color dose meter using the same

ABSTRACT

To detect an irradiated radiation efficiently, so that the dose can be measured with high sensitivity. A photochromic material comprising an illuminant(s) which emits a light when irradiated with a radiation and a diarylethene photochromic compound(s) having a specific structure, and a color dose meter employing it.

TECHNICAL FIELD

The present invention relates to a photochromic material useful formeasuring a radiation dose and a color dose meter employing it, wherebya radiation dose can simply be measured.

BACKGROUND ART

Irradiation treatment by means of X-rays, γ-rays, etc. has been commonfor the purpose of sterilization of medical equipments. In recent years,such treatment is applied also to blood for transfusion to prevent agraft-versus-host disease (GVHD) by blood transfusion.

To examine whether or not a necessary amount of radiation has beenirradiated to the object, it is common to adopt a method wherein anindicator containing a substance which undergoes a color changeirreversibly when irradiated with a radiation, is permitted to bepresent in the object to be irradiated, and after the irradiation, it istaken out, and the dose is ascertained by the color change.

For example, as an indicator for radiation sterilization of medicalequipments, one employing an oxidation-reduction dye such as a leuco dyeand a polyvinyl chloride, has been practically used. This indicatorundergoes a color change when irradiated with a radiation of at least5000 Gy.

However, the irradiation dose to blood for transfusion is usually at alevel of from 15 to 50 Gy, and therefore, the presence or absence ofsuch irradiation can not be detected by this indicator.

JP-A-2-201440 discloses, as an indicator which undergoes a color changewhen irradiated with a radiation of from 15 to 50 Gy, a radiationcolor-changeable composition having a metal such as calcium doped on analkali metal halide such as potassium chloride. However, it is generallyknown that a halide of an alkali metal is weak to moisture and has beendisadvantageous for use in a medical field where it is often in contactwith moisture. Further, it has had a drawback that the color-changedportion tends to undergo color fading due to an environmental light suchas a room light.

JP-A-2000-65934 discloses a dose meter comprising an organic compoundshowing an electron accepting property by a radiation and acolor-forming electron releasing organic compound. However, thedisclosed electron releasing organic compound is generally known to besusceptible to the influence of moisture or impurities in air, and therehas been a drawback that the dose meter employing it is poor in thestorage stability. Further, such an indicator can not be decolored andin many cases can not be re-used.

It has been proposed to use, for a dose meter, a photochromic compoundwhich shows sensitivity to a radiation and which is easy to handle.

For example, JP-A-2-216493 discloses a radiation-sensitive display sheetmade of a laminate having a layer containing a scintillator which emitsfluorescence and a layer containing a diarylethene compound whichundergoes a color change in response to the fluorescence emitted by thisscintillator. However, a maleic anhydride type diarylethene compoundsuch as 2,4,5-trimethylthienylmaleic anhydride used in this reference isinadequate in the sensitivity to a radiation. Further, the maleicanhydride moiety undergoes hydrolysis by moisture, and there has been adrawback that the storage stability is poor.

JP-A-11-258348 discloses a dose meter employing a heat irreversiblediarylethene compound. By using the thermally stable and reversiblediarylethene compound disclosed in this publication, even a radiationhaving a relatively low dose can accurately be measured. However, it hasbeen necessary to increase the thickness substantially, in order tomeasure the radiation at a low dose at a level of from 15 to 50 Gy whichis a common dose to blood for transfusion.

It is an object of the present invention to provide an indicator whichcan be used without being influenced by the environment and which has agood storage stability and is capable of detecting a radiation even at alow dose.

DISCLOSURE OF THE INVENTION

As a result of an extensive study, the present inventors have found itpossible to solve the above-mentioned problems by using in combination adiarylethene compound(s) (a photochromic compound(s)) having a certainspecific structure and an illuminant(s) which emits a light whenirradiated with a radiation. Namely, the gist of the present inventionresides in a photochromic material comprising an illuminant(s) whichemits a light when irradiated with a radiation, and a diarylethenecompound(s), wherein the diarylethene compound(s) is represented by thefollowing formula (0), and the absorption spectrum of the ring openedform or the ring closed form of the diarylethene compound(s), and theemission spectrum of the illuminant(s), overlap each other:

in the above formula (0), each of groups R¹ and R² which are independentof each other, is an alkyl group, a cycloalkyl group or an alkoxy group,each of groups X¹, X², Y¹ and Y² which are independent of one another,is either one of

group R³ is a hydrogen atom, an alkyl group which may be substituted, anaryl group which may be substituted, or a cycloalkyl group which may besubstituted,

group R⁴ is a hydrogen atom, an alkyl group which may be substituted, ora cycloalkyl group which may be substituted,

ring D¹ is a 5- or 6-membered aromatic ring which is formed by groups X¹and Y² together with two carbon atoms bonded thereto and which may besubstituted, and ring E¹ is a 5- or 6-membered aromatic ring which isformed by groups X² and Y² together with two carbon atoms bonded theretoand which may be substituted,

rings D¹ and E¹ may further have a 5- or 6-membered aromatic ring whichmay be substituted, condensed thereto.

Further, another gist of the present invention resides in a color dosemeter prepared by using such a photochromic material.

In this specification,

has the same meaning as

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view which schematically shows an embodimentof a layered structure of a laminate as a color dose meter of thepresent invention.

FIG. 2 is a cross-sectional view which schematically shows anotherembodiment of a layered structure of a laminate as a color dose meter ofthe present invention.

FIG. 3 is a view illustrating the overlapping of the emission spectrumof the illuminant and the absorption spectrum of the diarylethenecompound. The solid line shows the absorption spectrum of thediarylethene compound, and the dotted line shows the emission spectrumof the illuminant.

FIG. 4 is views illustrating embodiments of a seal-form color dose meterof the present invention. (a) shows a front view, and (b) shows across-sectional view.

FIG. 5 is a view showing an embodiment of a tag-form color dose meter ofthe present invention.

DESCRIPTION OF SYMBOLS

-   -   1, 1′: support layer    -   2, 2′: emission layer    -   3: photochromic layer    -   4: photochromic material    -   5: light blocking substrate    -   5′: ultraviolet absorptive transparent substrate    -   6: adhesive layer or double-stick tape    -   7: release paper    -   8: ultraviolet absorptive transparent film    -   9 opening or transparent portion containing an ultraviolet        absorber    -   10, 11: laminate (color dose meter)    -   20: tag-form color dose meter    -   30: blood bag

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be described in further detail.

(1) Construction of the Photochromic Material

(1-1) Diarylethene Compound(s)

As mentioned above, the diarylethene compound(s) means a compound(s)which undergoes an isomerization reaction when irradiated with a lightor radiation.

The diarylethene compound(s) to be used in the present invention, is acompound(s) represented by the above formula (0).

Here, substituents which rings D and E in the formula (0) may have, arenot particularly limited, but may preferably be various groups whichwill be described hereinafter as groups R¹³, R¹⁵ to R¹⁷, R²³, and R²⁵ toR²⁷.

Further, when an aromatic ring is further condensed to ring D or E, sucha condensed ring may have substituents such as an alkenyl group, analkoxy group, an alkoxyalkoxy group, an allyloxy group, an aryl group,an aryloxy group, a heteroaryl group, a halogen atom, a hydroxyl group,a carboxyl group, a carbonyl group, a cyano group and a nitro group.

The compound represented by the above formula (0) may, preferably, be acompound represented by the following formula (I) or (II):

In the above formula (I), each of groups R¹¹ and R¹² which areindependent of each other, is an alkyl group, a cycloalkyl group or analkoxy group.

Further, each of groups X¹¹ and X¹² which are independent of each other,is either one of

but among them, preferred are

Further, each of groups Y¹¹ and Y¹² which are independent of each other,is either one of

In the above respective formulae, group R¹³ is a hydrogen atom, an alkylgroup which may be substituted, an aryl group which may be substituted,or a cycloalkyl group which may be substituted, but among them, ahydrogen atom, an alkyl group which may be substituted, or an aryl groupwhich may be substituted, is preferred. Further, group R¹⁷ isindependently a hydrogen atom, an alkyl group which may be substituted,or a cycloalkyl group which may be substituted.

Each of groups R¹⁵ and R¹⁶ which are independent of each other, is ahydrogen atom, an alkyl group which may be substituted, an aryl groupwhich may be substituted, a heteroaryl group which may be substituted,or a cycloalkyl group which may be substituted.

When groups R¹⁵ and R¹⁶ are an alkyl group, an aryl group, a heteroarylgroup or a cycloalkyl group, substituents which these groups may have,may, for example, be an alkenyl group, an alkoxy group, an alkoxyalkoxygroup, an allyloxy group, an aryl group, a heteroaryl group, an aryloxygroup, a halogen atom, a hydroxyl group, a carboxyl group, a carbonylgroup, a cyano group and a nitro group.

When group Y¹¹ and/or group Y¹² is

group R¹⁵ and/or group R¹⁶ may be bonded to group R¹⁷ to form a 5- or6-membered aromatic ring.

Substituents which such an aromatic ring may have, may, for example, bean alkenyl group, an alkoxy group, an alkoxyalkoxy group, an allyloxygroup, an aryl group, a heteroaryl group, an aryloxy group, a halogenatom, a hydroxyl group, a carboxyl group, a carbonyl group, a cyanogroup and a nitro group.

In the above formula (II), each of groups R²¹ and R²² which areindependent of each other, is an alkyl group, a cycloalkyl group or analkoxy group.

Further, each of groups X²³ and X²⁴ which are independent of each other,is either one of

Further, each of groups Y²¹ and Y²² is either one of

Further, each of groups R²⁵ and R²⁶ which are independent of each other,is a hydrogen atom, an alkyl group which may be substituted, an arylgroup which may be substituted, a heteroaryl group which may besubstituted, or a cycloalkyl group which may be substituted.

Here, when group Y²¹ and/or group Y²² is

group R²⁵ and/or group R²⁶ may be bonded to R²⁷ to form a 5- or6-membered aromatic ring.

Substituents which the aromatic ring may have, may, or example, be analkenyl group, an alkoxy group, an alkoxyalkoxy group, an allyloxygroup, an aryl group, a heteroaryl group, an aryloxy group, a halogenatom, a hydroxyl group, a carboxyl group, a carbonyl group, a cyanogroup and a nitro group.

Further, in the above formula (II), group R²³ is a hydrogen atom, analkyl group which may be substituted, an aryl group which may besubstituted, or a cycloalkyl group which may be substituted, but, amongthem, a hydrogen atom, an alkyl group which may be substituted, or anaryl group which may be substituted, is preferred. Further, group R²⁷ isa hydrogen atom, an alkyl group which may be substituted, or acycloalkyl group which may be substituted.

In the above formula (II), when groups R²⁵ and R²⁶ are an alkyl group,an aryl group, a heteroaryl group or a cycloalkyl group, substituentswhich these groups may have, may, for example, be an alkenyl group, analkoxy group, an alkoxyalkoxy group, an allyloxy group, an aryl group, aheteroaryl group, an aryloxy group, a halogen atom, a hydroxyl group, acarboxyl group, a carbonyl group, a cyano group and a nitro group.

Specific examples of rings D¹ and E¹ in the formula (I) will be shownbelow, but they are not limited to such specific examples.

In the above formulae, R¹³ is as defined in the above formula (I), andR²⁷ is as defined in the above formula (II).

Among them, the following ones are preferred as the hetero ringcontaining groups X¹¹ and Y¹¹, and as the hetero ring containing groupsX¹² and Y¹²:

In the above formulae, the benzene ring condensed to a hetero ring is aring formed by the bonding of group R¹⁵ or R¹⁶ to group R¹⁷.

Further, preferred as the hetero ring containing groups X²¹ and Y²¹ orthe hetero ring containing groups X²² and Y²², in the above formula(II), are the following ones:

In the above formulae, the benzene ring condensed to a hetero ring, is aring formed by the bonding of group R²⁵ or R²⁶ to group R²⁷.

Specific examples of the compound(s) represented by the above formula(I) will be shown below, but the present invention is by no meansrestricted thereto.

Specific examples of the compound(s) represented by the above formula(II) will be shown below, but the present invention is by no meansrestricted thereto.

Various diarylethene compounds shown above, can be produced optionallyby means of conventional techniques. For example, they can be preparedby techniques optionally selected from those disclosed in e.g.JP-A-9-241625.

Further, in the photochromic material of the present invention,diarylethene compounds may be used alone or may be used in combinationas a mixture of a plurality of them. When they are used in combination,a plurality of them may be selected from a group of compoundsrepresented by either one of the above formulae (I) and (II), or atleast one type may be selected for use from the respective groups ofcompounds represented by the above formulae (I) and (II). Further, anoptional compound other than the group of compounds represented by theabove formula (I) or (II) may be used in combination.

The diarylethene compound(s) to be used in the present invention ispreferably one showing a heat irreversibility. In the present invention,“heat irreversibility” means that the half-life time of the ring closedform in an environment of 30° C. is at least 10 days. In a case wherethe diarylethene compound is not heat irreversible, it is likely thatthe ring closed form readily undergoes an isomerization reaction at roomtemperature and becomes to be a ring opened form, whereby the state ofthe color change formed by the irradiation of a radiation can not bestably maintained.

Further, in order to avoid coloration by an environmental light such asa room light, the quantum yield in the ring opening reaction ispreferably at most 10⁻³, more preferably at most 10⁻⁴, particularlypreferably at most 10⁻⁵.

(1-2) Illuminant(s)

The illuminant(s) to be used in the present invention is notparticularly limited with respect to its type, so long as it can beexcited to emit a light when irradiated with a radiation. The type ofthe radiation is not particularly limited, and various types such asultraviolet rays, X-rays, γ-rays, α-rays, β-rays, electron rays andneutron rays may, for example, be mentioned. Among them, in view of themain application to the after-mentioned color dose meter, theilluminant(s) to be used in the present invention is preferably onewhich can be excited to emit a light by a radiation having a wavelengthof from about 10⁻⁵ to 10 nm.

By a color dose meter employing a conventional diarylethene compound(s),it has been difficult to measure the dose of a radiation having awavelength shorter than ultraviolet rays, particularly a radiationhaving a strong transmitting power such as γ-rays, X-rays or neutronrays.

However, in the photochromic material of the present invention, anilluminant(s) comprising atoms usually having an atomic mass larger thana diarylethene compound(s), is used in combination, whereby it ispossible to efficiently capture a radiation. Further, by the energytransfer or the electron transfer from the illuminant(s) in an excitedstate, the isomerization reaction of the diarylethene compound(s) isaccelerated, whereby the sensitivity to a radiation of the photochromicmaterial will be improved (a sensitizing effect).

In the present invention, the type of the light emitted from theilluminant(s) is not particularly limited. However, as describedhereinafter, it is required to have an emission spectrum which overlapsan absorption spectrum of the ring opened form or the ring closed formof the diarylethene compound(s). In FIG. 3, the overlapping of theemission spectrum of the illuminant(s) and the absorption spectrum ofthe diarylethene compound(s), is shown schematically.

It is particularly preferably a phosphor (an ultraviolet light emittingphosphor) having an emission peak in the ultraviolet wavelength region,i.e. a phosphor which is considered to have an excitation energy levelhigher than the diarylethene compound. Particularly preferred is onewhich emits a light within the ultraviolet wavelength region with awavelength of from 10 to 400 nm.

Further, the illuminant(s) in the present invention is preferably aninorganic compound.

Further, from the viewpoint of the photochromic material of the presentinvention, the illuminant(s) is preferably one having a high sensitivityto a radiation and has a sufficiently large quantity of emission.Particularly preferred is an illuminant comprising so-called heavyatoms, since atoms having large atomic numbers (heavy atoms) usuallyhave high sensitivity to a radiation. Specifically, an illuminantcomprising elements having atomic numbers of at least 19, is preferred,and especially, an illuminant comprising elements having atomic numbersof at least 37, is more preferred.

As specific examples of the illuminant(s) to be used in the presentinvention, various illuminants used as practical phosphors may bementioned, including, for example, a halophosphate phosphor such as3Ca₃(PO₄)₂.Ca(F, Cl)₂:Sb³⁺, 3Ca₃(PO₄)₂.Ca(F, Cl)₂:Sb³⁺, Mn²⁺,Sr₁₀(PO₄)₆Cl₂:Eu²⁺, (Sr, Ca)₁₀(PO₄)₆Cl₂:Eu²⁺, (Sr,Ca)₁₀(PO₄)₆Cl₂.nB₂O₃:Eu²⁺, (Ba, Ca, Mg)₁₀(PO₄)₆Cl₂:Eu²⁺, a phosphatephosphor such as Sr₂P₂O₇:Sn²⁺, Ba₂P₂O₇:Ti⁴⁺, (Sr, Mg)₃(PO₄)₂:Sn²⁺,Ca₃(PO₄)₂:Tl²⁺, 2Sr O.0.84P₂O₅.0.16B₂O₃:Eu²⁺, LaPO₄:Ce³⁺, Tb³⁺,La₂O₃.0.2SiO₂.O. 9P₂O₅:Ce³⁺, Tb³⁺, Zn₃(PO₄)₂:Mn²⁺, or (Sr,Mg)₃(PO₄)₂:Cu⁺, a silicate phosphor such as Zn₂SiO₄:Mn²⁺, CaSiO₃:Pb²⁺,Mn²⁺, (Ba, Sr, Mg)₃Si₂O₇:Pb²⁺, (Ba, Mg, Zn)₃Si₂O₇:Pb²⁺, BaSi₂O₅:Pb²⁺, Sr₂Si₃O₈.2SrCl₂:Eu²⁺, Ba₃MgSi₂O₈:Eu²⁺, (Sr, Ba)Al₂Si₂O₈:Eu²⁺, Y₂S iO₅:Ce³⁺or Tb³⁺, a tungstate phosphor such as CaWO₄, CaW O₄:Pb²⁺, or MgWO₄, analuminate phosphor such as LiAlO₂:Fe³⁺, BaAl₈O₁₃:Eu²⁺, BaMgAl₁₀O₁₇:Eu²⁺,BaMgAl₁₀O₁₇:Eu²⁺, Mn²⁺, Sr₄Al₁₄O₂₅:Eu²⁺, SrMgAl₁₀O₁₇:Eu²⁺,CeMgAl₁₁O₁₉:Tb³⁺, CeMgAl₁₁O₁₉, (Ce, Gd)(Mg, Ba)Al₁₁O₁₉, Y₂O₃.Al₂O₃:Tb³⁺,or Y₃Al₅O₁₂:Ce³⁺, and others such as Y₂O₃:Eu³⁺, YVO₄:Eu³⁺, Y(P,V)O₄:Eu³⁺, YVO₄:Dy³⁺, Cd₂B₂O₅:Mn²⁺, SrB₄O₇:Eu²⁺, SrB₄O₇F:Eu²⁺,GdMgB₅O₁₀:Ce³⁺, Tb³⁺, 6MgO.As₂O₅:Mn⁴⁺, 3.5MgO.0.5MgF₂.GeO₂:Mn⁴⁺,MgGa₂O₄:Mn²⁺, ZnS:Ag, (Zn, Cd)S:Ag, (Zn, Cd)S:Cu, Al, ZnS:Ag, ZnS:Cu,Al, ZnS:Au, Cu, Al, CsI:Na, CsI:Tl, BaSO₄:Eu²⁺, Gd₂O₂S:Tb³⁺,La₂O₂S:Tb³⁺, Y₂O₂S:Tb³⁺, Y₂O₂S:Eu³⁺, LaOBr:Tb³⁺, LaOBr:Tm³⁺, BaFCl:Eu²⁺,BaFBr:Eu²⁺, HfP₂O₇, LiF, Li₂B₄O₇:Mn²⁺, CaF₂:Mn²⁺, CaSO₄:Mn²⁺,CaSO₄:Dy³⁺, Mg₂SiO₄:Tb³⁺, CaF₂:Eu²⁺, LiI:Eu²⁺, TlCl:Be, I, CsF, BaF₂,Bi₄Ge₃O₁₂, Kl:Tl, CaWO₄, and CdWO₄. These illuminants can be optionallyprepared by means of known techniques. Most of these illuminants containthe above-mentioned elements having atomic numbers of at least 19 orelements having atomic numbers of at least 37, whereby the sensitivityto a radiation is high, and the quantity of emission is sufficientlylarge. Among these, particularly preferred are ultraviolet-emittingphosphors such as Ca₃(PO₄)₂:Tl⁺, (Ca, Zn)₃(PO₄)₂:Tl⁺, SrMgP₂O₇:Eu²⁺,SrB₄O₇F:Eu²⁺, (Ba, Sr, Mg)₃Si₂O₇:Pb²⁺, (Ba, Mg, Zn)₃Si₂O₇:Pb²⁺,BaSi₂O₅:Pb²⁺, (Sr, Ba)Al₂Si₂O₈:Eu²⁺, CeMgAl₁₁O₁₉, (Ce, Gd) (Mg,Ba)Al₁₁O₁₉, SrB₄O₇:Eu²⁺, CsF, BaF₂, BaSO₄:Eu²⁺, BaFCl:Eu²⁺, BaFBr:Eu²⁺,HfP₂O₇, and LiF.

As the illuminant(s) to be used in the present invention, one havinghigh luminous efficiency to irradiated light is preferred. Namely, forexample, in a case where the photochromic material of the presentinvention is used for a color dose meter which will be describedhereinafter, the illuminant(s) is preferably one having high luminousefficiency to stimulation by a light having a wavelength to be detected.

Further, the higher the density of the illuminant, the higher theability to capture the light to be detected, such being preferred.Further, the illuminants represented by the above-mentioned variousphosphors may be used alone or in combination as a mixture of aplurality of them.

(1-3) Combination of the Diarylethene Compound(s) and the Illuminant(s)

The photochromic material of the present invention is characterized inthat the diarylethene compound(s) and the illuminant(s) are selected forcombination so that part or whole of the emission spectrum of theilluminant(s) will overlap the absorption spectrum of the ring openedform or the ring closed form of the diarylethene compound(s).

By such a construction, in a case where the photochromic material of thepresent invention is used for a color dose meter, firstly, byirradiation of a radiation, electrons of the illuminant(s) will be in anexcited state, and the energy or photons will transfer from such anexcited state to an excited state of the diarylethene compound(s),whereby an isomerization reaction of the diarylethene compound(s) willtake place. As a result, the photochromic material undergoes a colorchange, whereby the irradiated radiation can efficiently be detected,and it will be possible to measure the dose with high sensitivity.

For example in the case of the diarylethene compound(s), a light withinan ultraviolet wavelength region with a wavelength of from 10 to 400 nmis preferred in order to let the isomerization reaction from the openring form take place efficiently. Accordingly, as the illuminant(s) inthe present invention, one having the emission peak mainly in thisultraviolet wavelength region (i.e. the above-mentionedultraviolet-emitting phosphor) is preferred. It is preferred that theemission spectrum of the illuminant(s) and the absorption bandcontaining the maximum absorption wavelength of the ring opened form orthe ring closed form of the diarylethene compound(s), overlap each otherover a wavelength range as wide as possible.

Further, it is preferred that the emission spectrum of the illuminant(s)overlaps the absorption spectrum of the ring opened form of thediarylethene compound(s), because the ring opened form usually has anabsorption in the wavelength region of the radiation, the quantum yieldis higher in the ring closing reaction than in the ring-opening reactionin many cases, and the ring closed form has a deep visible color thanthe ring opened form in many cases, whereby it is easier to detect theexposure by the formation of the ring closed form.

Further, in the photochromic material of the present invention,illuminants may be used alone or in combination as a mixture of two ormore of them. Especially when the absorption spectrum peak of thediarylethene compound is sharp, if the same illuminant is used, a strongemission can be obtained at a specific wavelength range, and thesensitivity in detection of the radiation can be increased. On the otherhand, in a case where the absorption spectrum peak of the diarylethenecompound is broad, if two or more illuminants showing emissions atdifferent wavelength ranges, are used in combination, an emission can beobtained within a wide wavelength range, whereby a radiation within awide wavelength range can efficiently be detected.

(2) Mode of the Photochromic Material and the Color Dose Meter

The photochromic material of the present invention is not particularlylimited so long as it is in a mode wherein the above-mentioneddiarylethene compound(s) and the illuminant(s) act on each othermutually. However, it is particularly preferred to constitute it as acomposition comprising the above-mentioned diarylethene compound(s) andthe illuminant(s) or as a laminate comprising a layer containing theabove-mentioned diarylethene compound(s) and a layer containing theilluminant(s).

Here, the former composition is broadly meant for a solid and a liquid,in which the above-mentioned diarylethene compound(s) and theilluminant(s) are contained in a mixed state. Specifically, a solutionor dispersion of the diarylethene compound(s) prepared by dissolving ordispersing the above diarylethene compound(s) and dispersing also theilluminant(s), a resin composition containing the above-mentioneddiarylethene compound(s) and the illuminant(s), or a molded productprepared by mixing the diarylethene compound(s) and the illuminant(s) insolid states, may, for example, be mentioned. The photochromic materialsof the present invention constructed in the above respectiveembodiments, can be used as color dose meters, respectively, in suchmanners as depending on the respective embodiments.

Now, since embodiments of the photochromic material of the presentinvention and their applications as color dose meters will be describedin detail.

(2-1) Solution or Dispersion

A solution or dispersion of the diarylethene compound(s) as anembodiment of the photochromic material of the present invention can beprepared by dissolving or dispersing the above-mentioned diarylethenecompound(s) in a solvent or in a dispersing medium and at the same time,dispersing the above-mentioned illuminant(s) in the above-mentionedsolvent or dispersing medium.

The solvent (dispersing medium) is not particularly limited so long asit is capable of dissolving or dispersing the above-mentioneddiarylethene compound(s) and it does not hinder detection of the colorchange of the diarylethene compound(s) by exposure to a radiation whenused as a color dose meter. Specifically, various organic solvents maybe mentioned, including an aromatic solvent such as benzene or toluene,an aliphatic solvent such as hexane, an ether solvent such astetrahydrofuran (THF), and a chlorine type solvent such as chloroform.Among them, an aromatic solvent such as benzene or toluene is preferred.

In the above solvent (dispersing medium), the above-mentioneddiarylethene compound(s) is dissolved or dispersed, and at the sametime, the above-mentioned illuminant(s) is dispersed to obtain thesolution or dispersion of the diarylethene compound(s). The amount ofthe diarylethene compound(s) is preferably within a range of from 10⁻⁵to 10 mol/l in the solution or dispersion, and the amount of theilluminant(s) is preferably within a range of from 0.5 to 100 parts byweight per 100 parts by weight of the solution or dispersion. Further,in a case where the above-mentioned diarylethene compound(s) and theilluminant(s) are to be dispersed, a known dispersing agent or the likemay further be incorporated.

The solution or dispersion of the diarylethene compound(s), thusprepared, is sealed in a quartz cell or the like containing noimpurities, to obtain a color dose meter. When the prepared cell isexposed to a radiation, the color of the solution or dispersion changesdepending upon the dose of the radiation. This absorption, transmissionor reflection spectrum is measured, and the change in the absorbance,transmittance or reflectance is determined, whereby the dose of theradiation can be estimated.

(2-2) Resin Composition

The resin composition as one embodiment of the photochromic material ofthe present invention can be prepared, for example, (a) by dissolving(dispersing) the above-mentioned diarylethene compound(s) and theilluminant(s) in a solvent (dispersing medium) together with a baseresin, or (b) by dissolving (dispersing) the above-mentioneddiarylethene compound(s) and the illuminant(s) directly in the baseresin.

The base resin is not particularly limited so long as it is capable ofsuitably dissolving or dispersing the above-mentioned diarylethenecompound(s). Specifically, an acrylic resin, a methacrylic resin, avinyl acetate resin, a vinyl chloride resin, a polyethylene resin, apolypropylene resin, a polystyrene resin, a polynaphthalene resin, apolycarbonate resin, a polyethylene terephthalate resin or a polyvinylbutyral resin, may, for example, be mentioned.

The solvent (dispersing medium) in the above method (a) is notparticularly limited so long as it is capable of suitably dissolving ordispersing the above base resin and it does not hinder the film formingprocess. Specifically, various organic solvents may be mentioned,including, for example, an aromatic solvent such as benzene or toluene,an aliphatic solvent such as hexane, an ether solvent such as THF, achlorine type solvent such as chloroform, and a ketone solvent such asmethyl ethyl ketone.

To this solvent (dispersing medium), the base resin and theabove-mentioned diarylethene compound(s) are dissolved or dispersed, andthen, the above-mentioned illuminant(s) is added and dispersed toprepare the resin composition. The amount of the diarylethenecompound(s) is preferably within a range of from 0.2 to 200 parts byweight per 100 parts by weight of the base resin, and the amount of theilluminant(s) is preferably within a range of from 1 to 2000 parts byweight, more preferably within a range of from 5 to 2000 parts byweight, per 100 parts by weight of the base resin. Further, a knowndispersant(s), antioxidant(s), oxygen-trapping agent(s), plasticizer(s)or the like, may be added.

On the other hand, in the case of the above method (b), theabove-mentioned diarylethene compound(s) and the illuminant(s) aredirectly kneaded into the above base resin to prepare the resincomposition.

The resin composition thus prepared may be formed into a film or a rodby means of a known method such as injection molding, extrusion moldingor heat pressing, to obtain a color dose meter. Especially, in the caseof processing into a film, the film-forming processing can be carriedout by means of various known techniques such as a casting method, aspin coating method, a bar coater method, a die cast method, etc. Thethickness of the film is not particularly limited so long as it does notdepart from the purpose for the color dose meter, but it is preferablywithin a range of from 0.01 to 10 mm.

When the resin composition thus formed is exposed to a radiation, thecolor will change depending upon the dose of the radiation. Thisabsorption, transmission or reflection spectrum is measured, and thechange in the absorbance, transmittance or reflectance is determined,whereby the dose of the radiation can be estimated.

(2-3) Molded Product

The molded product as one embodiment of the photochromic material of thepresent invention can be prepared by mixing the solid diarylethenecompound(s) and the solid illuminant(s), and compressing this mixture tomold it into a solid having a specific shape.

Specifically, the illuminant powder having the particle size adjusted toa median particle diameter of from about 10 nm to 50 μm, theabove-mentioned diarylethene compound(s) having the particle sizeadjusted to a median particle diameter of from 10 nm to 100 μm, and, ifnecessary, a binder, are thoroughly mixed, and then, the mixed powder isfilled in a mold, followed by compression molding under a pressure offrom 1 MPa to 1 GPa. If the median particle diameter of theilluminant(s) is smaller than 10 nm, the powder tends to beagglomerated, whereby there may be a case where no adequate mixing withthe diarylethene compound(s) can be made. On the other hand, if themedian particle diameter exceeds 50 μm, there may be a case where itbecomes difficult to maintain the shape as a molded product.

The median particle diameter of the diarylethene compound(s) is usuallyfrom about 10 nm to 100 μm, but it is preferably a particle size wherebythe compound(s) can readily penetrate into spaces of the illuminant(s).Accordingly, it is more preferably from about 10 nm to 50 μm.

The binder to be used is not particularly limited so long as it is onecommonly known as a binder to be used for inorganic powders.Specifically, not only inorganic binders such as a water-solublesubstance such as water glass, a sol substance such as silica sol oralumina sol, and various cements which undergo hydration reactions, butalso organic binders such as nitrocellulose, cellulose acetate,ethylcellulose, polyvinyl butyral, a vinyl chloride/vinyl acetatecopolymer, a polyalkyl (meth)acrylate, polycarbonate, polyurethane,cellulose acetate butyrate, polyvinyl alcohol, gelatin, a polysaccharidesuch as dextrin, and gum arabic, may be mentioned.

With respect to the shape of the molded product, one having an optionalshape may be used depending upon the shape to be used as a color dosemeter.

For example, in a case where the color dose meter is used in a flatplate shape, the mixed powder is filled in a mold and then compressed bymeans of a single screw extruder or a twin screw extruder to mold itinto a flat plate shape. Further, in the case of molding into a complexshape, the mixed powder is filled into a rubber mold having a complexshape and then compressed by means of a hydraulic pressing machine tomold it into the complex shape.

The compression molding pressure is preferably from 1 MPa to 1 GPa. Ifthe pressure is less than 1 MPa, no adequate mechanical strength tendsto be imparted, whereby it is likely that the molded product can notmaintain its shape. On the other hand, if the pressure is higher than 1GPa, an installation more than necessary for the molding will berequired, whereby an extra cost is likely to be incurred.

On the other hand, it is possible to prepare a molded product made of asintered body having a high strength, by impregnating or coating theabove-mentioned diarylethene compound to a sintered body obtained bymolding and firing the illuminant powder.

In this case, firstly, the illuminant powder adjusted to theabove-mentioned particle size and, if necessary, the above-mentionedbinder, are thoroughly mixed and compression-molded, and then the moldedproduct is fired under the firing conditions suitable for the type ofthe illuminant. On the surface of the dense sintered body thus obtained,the above-mentioned diarylethene compound(s) is coated, or theabove-mentioned diarylethene compound(s) is impregnated into theinterior of the porous sintered body thus obtained. Such coating orimpregnation is carried out by dissolving or dispersing theabove-mentioned diarylethene compound(s) in a suitable solvent.

The firing conditions suitable for the type of the illuminant(s) arepreferably conditions close to the firing temperature, retention timeand atmosphere employed at the time of preparing the illuminant powder.A preferred firing temperature range is from 500 to 1900° C., and theretention time is from 10 minutes to 48 hours. The atmosphere isoptionally adjusted to be e.g. an oxidizing atmosphere, a reducingatmosphere or a sulfiding atmosphere, depending upon the composition ofthe illuminant(s) and the type of the luminescent ions.

The molded product thus molded into a desired shape such as a filmshape, a rod-shape or a plate shape, can be used as it is, as a colordose meter. When the molded product thus prepared is exposed to aradiation, the color of the molded product will change depending uponthe dose of the radiation. This absorption, transmission or reflectionspectrum is measured, and the change in the absorbance, transmittance orreflectance is determined, whereby the dose of the radiation can beestimated.

(2-4) Laminate

The laminate as one embodiment of the photochromic material of thepresent invention comprises at least a layer containing theabove-mentioned diarylethene compound(s) and a layer containing theilluminant(s).

Here, examples of the layered structure of the laminate will bedescribed with reference to FIGS. 1 and 2, but the layered structure isby no means restricted thereto. Here, each of FIGS. 1 and 2 is across-sectional view schematically illustrating an example of thelayered structure of a laminate.

In the example of the layered structure shown in FIG. 1, a luminescentlayer 2 containing the above-mentioned illuminant(s) is formed on asupport 1, and a photochromic layer 3 containing the above-mentioneddiarylethene compound(s) is formed on the luminescent layer 2, toprepare a laminate 10. Further, two such laminates 10 may be prepared,and the two laminates 10 may be bonded so that the surfaces of thesupports 1 will face each other, to form a single laminate (not shown).

In the layered structure shown in FIG. 2, firstly, in the same manner asin the example shown in FIG. 1, a laminate having the support 1, theluminescent layer 2 and the photochromic layer 3 sequentially laminated,is prepared. Then, a luminescent layer 2′ is formed on a separatelyprepared support 1′, followed by bonding so that this luminescent layer2′ will face the photochromic layer 3 of the former, to prepare a newlaminate 11.

The material for the supports 1 and 1′ is not particularly limited solong as it is capable of securing the stability of the shapes of theluminescent layers 2 and 2′ and the photochromic layer 3 and it will notimpair the purpose of the color dose meter of the present invention.

Specifically, a resin such as cellulose acetate, cellulose propionate,cellulose acetate butyrate, a polyester such as polyethyleneterephthalate, polystyrene, polymethyl methacrylate, polyamide,polyimide, a vinyl chloride/vinyl acetate copolymer or polycarbonate,formed into a film, a baryta paper, a resin coated paper, a normalpaper, or an aluminum alloy foil, may, for example, be mentioned. In acase where a material such as a resin film or paper is to be used, alight-absorbing substance such as carbon black, or a light-reflectingsubstance such as titanium dioxide or calcium carbonate, may directly bekneaded into such a material for preliminarily mixing.

The luminescent layers 2 and 2′ may be prepared for example, by mixing aproper amount of the illuminant(s) with a binder, adding an organicsolvent thereto to prepare an illuminant coating fluid having a suitableviscosity, coating this coating fluid on the support 1 or 1′ by a knifecoater or a roll coater, followed by drying.

Further, to this illuminant coating fluid, a dispersing agent such asphthalic acid or stearic acid, or a plasticizer such as triphenylphosphate or diethyl phthalate, may be added, as the case requires. Thebinder is not particularly limited so long as it is one commonly knownas a binder for an illuminant. Specifically, nitrocellulose, celluloseacetate, ethyl cellulose, polyvinyl butyral, linear polyester, polyvinylacetate, a vinylidene chloride/vinyl chloride copolymer, a vinylchloride/vinyl acetate copolymer, polyalkyl (meth)acrylate,polycarbonate, polyurethane, cellulose acetate butyrate, polyvinylalcohol, gelatin, a polysaccharide such as dextrin, or gum arabic, maybe mentioned.

Further, the organic solvent is not particularly limited so long as itis capable of dispersing the illuminant. For example, an alcohol solventsuch as ethanol, an ether solvent such as methyl ethyl ether, a ketonesolvent such as methyl ethyl ketone, an ester solvent such as butylacetate or ethyl acetate, or an organic solvent such as xylene, may bementioned. The final weight of the illuminant(s) coated on the support 1or 1′ is usually preferably from 30 to 200 mg/cm². If the coated weightis less than 30 mg/cm², the sensitivity to a radiation tends todeteriorate, and inversely, if it exceeds 200 mg/cm², the sensitivity tothe radiation is saturated, whereby no further improvement may beobtained in the sensitivity of the dose meter.

The photochromic layer 3 is prepared by dissolving the diarylethenecompound(s) in an organic solvent, if necessary, together with e.g. abase resin and processing it into a film by means of a known techniquesuch as a casting method or a spin coating method.

In a case where a base resin is to be used, such a base resin is notparticularly limited so long as it is capable of dissolving ordispersing the diarylethene compound. Specifically, any one of the baseresins mentioned in the section for (2-2) resin composition, such as apolystyrene resin, a polycarbonate resin, etc., may be mentioned.

The amount of the diarylethene compound(s) is preferably from 0.1 to 50parts by weight per 100 parts by weight of the base resin.

The organic solvent is not particularly limited so long as it is capableof dissolving or dispersing the diarylethene compound(s) and capable ofdissolving the base resin. Specifically, any one of those mentioned inthe section of (2-2) resin composition, such as toluene, THF, etc., maybe used. Otherwise, the diarylethene compound(s) may directly be kneadedinto the base resin, followed by processing into a film by means of aconventional technique such as an extrusion molding method or aninjection molding method.

The thickness of the layer is preferably within a range of from 0.01 to10 mm.

Further, between the support 1 or 1′ and the luminescent layer 2 or 2′,a light reflecting layer, a light absorbing layer or a metal foil layermay, for example, be formed, as the case requires. In such a case, alight-reflecting layer, a light-absorbing layer or a metal foil layermay preliminarily be formed on the support 1 or 1′, and theabove-mentioned illuminant coating fluid is coated and dried thereon toform the luminescent layer 2 or 2′.

Further, a protective film may be formed, as the case requires, on thesurface of the luminescent layer 2 or 2′ which is in contact with thephotochromic layer 3.

The protective layer may be formed by dissolving a resin such as acellulose derivative such as cellulose acetate, nitrocellulose,cellulose acetate butyrate, polyvinyl chloride, polyvinyl acetate, avinyl chloride/vinyl acetate copolymer, polycarbonate, polyvinylbutyral, polymethyl methacrylate, polyvinyl formal or polyurethane, in asolvent to prepare a protective film-coating fluid having a properviscosity, and coating and drying this on the previously formedluminescent layer 2 or 2′. Otherwise, a preliminarily formed protectivelayer, such as a transparent film made of e.g. polyethyleneterephthalate, polyethylene, polyvinylidene chloride or polyamide, maybe laminated on the previously formed luminescent layer 2 or 2′.

Further, in such a case, the luminescent layer 2 or 2′ may be producedby a method different from the above-mentioned production method.Namely, a protective film may preliminarily be formed on a flat supportsubstrate, and a luminescent layer 2 or 2′ may be formed thereon, andthis is peeled together with the protective film from the supportsubstrate and transferred onto the support 1 or 1′.

In the case of the layered structure shown in FIG. 2, the illuminants tobe used for the luminescent layers 2 and 2′ may be the same ordifferent.

In the layered structure shown in FIG. 2, it is preferred that at leastone of the supports 1 and 1′ is made of a colorless transparentmaterial, so that the color change of the photochromic layer 3 due toexposure to a radiation can be visually observed or measured from theexterior of the laminate 11. In such a case, it is preferred to applytreatment to prevent ultraviolet rays which will be describedhereinafter, to the transparent support.

The above layered structures of laminates 10 and 11 described withreference to FIGS. 1 and 2 are merely preferred examples, and as otherexamples, countless layered structures are in principle possible bylaminating the above-described respective layers (in addition to thesupport 1 or 1′, the luminescent layer 2 or 2′ and the photochromiclayer 3, as shown, the light-reflective layer, the light-absorbinglayer, the metal foil layer, the protective layer, etc.) in optionalcombinations and orders and if necessary, by adding new layers.

The laminate 10 or 11 thus prepared, may be used as a color dose meter,as it is, or, if necessary, after molding it. When the laminate 10 or 11thus prepared, is exposed to a radiation, it undergoes a color changedepending upon the dose of the radiation. By measuring the absorption,transmission or reflection spectrum of the laminate and determining thechange in the absorbance, transmittance or reflectance mechanically orby visual observation, the dose of the radiation can be estimated.

Further, in the above-described laminate 10 and 11, the respectivelayers may be constructed to be separable rather than bonded them.

Specifically, in the layered structure in FIG. 2, if the luminescentlayers 2 and 2′ and the photochromic layer 3 are constructed not to bebonded to each other, the laminate 11 can be separated into a portioncomprising the support 1 and the luminescent layer 2, a portioncomprising the support 1′ and the luminescent layer 2′, and a portioncomprising the photochromic layer 3. After exposing to a radiation in astate where these portions are all laminated, only the portioncomprising the photochromic layer 3 is taken out to measure the colorchange, whereby it is unnecessary to measure the color change of thephotochromic layer 3 present at the center of the laminate 11 fromoutside, and the supports 1 and 1′ and the luminescent layers 2 and 2′can be constructed to be sufficiently thick, and further, it will bepossible to further increase the sensitivity in detecting the radiation.

Among the above-described embodiments of the photochromic material ofthe present invention, the compounds represented by (2-1) to (2-3) arepreferred from such a viewpoint that the energy transfer or the electrontransfer from the luminant(s) excited by the radiation to thediarylethene compound(s) is easy, and (2-2) resin composition or (2-3)molded product is preferred from the viewpoint of the productionefficiency and handling efficiency when formed into a color dose meter.Most preferred is (2-2) resin composition.

To the photochromic material of the present invention, an ultravioletabsorber(s) may further be incorporated.

Specifically, in a case where the photochromic material is thecomposition represented by the above (2-1) to (2-3), it may beincorporated as one component of the composition, or an ultravioletblocking layer may be formed on the surface of a color dose meter formedby using such a composition.

Further, in a case where the photochromic material is a laminate, theultraviolet absorber(s) may be incorporated in a layer constituting sucha laminate, or an ultraviolet blocking layer may further be laminated onthe incident side of the radiation for detection in the laminate.

The ultraviolet blocking layer is preferably one capable of blocking alight having a wavelength of from 10 to 450 nm. In the presentinvention, “blocking” a light having a wavelength of from 10 to 450 nmmeans that the light transmittance in that wavelength range is made tobe at most 5%, preferably at most 3%.

By providing such a layer or by incorporating such an ultravioletabsorber(s), it is possible to prevent the reaction of the compound(s)by ultraviolet rays contained in e.g. an environment light other thanthe reaction by the radiation to be detected, whereby precision indetecting the dose will be improved.

In order to absorb a light having a wavelength of from about 380 to 450nm, contained in the environment light, it is preferred to use a dye(s)having an absorption in such a wavelength range, i.e. a yellow dye(s),in combination. Such a dye(s) is not particularly limited, and forexample, OIL YELLOW 3G, manufactured by Orient Chemical Industries,Ltd., Neptune (TM) Gelb 075, manufactured by BASF, or MACROLEX YELLOW 6Gmanufactured by BAYEL LTD., may, for example, be mentioned. Such a dyeis preferably an oil-soluble resin which is readily compatible with anorganic solvent or a resin, from the viewpoint of its practical form.

In order to prevent the performance deterioration and the influence overthe precision in detecting the dose by an environmental light, a lightin a wavelength region exceeding a wavelength of 450 nm may be blockedto some extent. However, by blocking a light in the visible lightwavelength region, the layer tends to be colored, whereby the colorchange at the display portion in the color dose meter is likely to behardly distinguished.

It is more preferred to provide a layer to block a light with awavelength of from 230 to 420 nm, within which the maximum absorptionwavelength of the ring opened form is present with respect to manydiarylethene type diarylethene compounds.

The method for forming the ultraviolet blocking layer is notparticularly limited, and such a layer may suitably be formed dependingupon the form of the color dose meter. For example, it may be formed bycoating, drying and curing a composition containing a known ultravioletabsorber(s) on the surface of a color dose meter, or a film containingan ultraviolet absorber(s) may be preliminarily formed, and such a filmmay be bonded to the surface of the dose meter.

The thickness of the ultraviolet blocking layer is preferably within arange of from about 0.01 μm to 500 μm.

As the ultraviolet absorber to be contained in the ultraviolet blockinglayer or as the ultraviolet absorber to be contained in the compositionas one embodiment of the photochromic material of the present invention,a known compound of e.g. a benzophenone type, a benzotriazole type or anaryl ester type may be mentioned.

Specifically, for example, UVINUL D-49 and UVINUL D-50, manufactured byBASF; Kemisorb 1011 and Kemisorb 1001, manufactured by Chemipro KaseiKaisha, Ltd.; MARK LA-51 and MARK LA-31, manufactured by ADECA ARGUSKagaku K.K.; Sumisorb 250 manufactured by Sumitomo Chemical Co., Ltd.;UVA 101 manufactured by Takemoto Oil & Fat Co., Ltd.; Tinuvin 213,Tinuvin 327 and Tinuvin 1577, manufactured by Ciba Specialty Chemicals,Inc., and Sandouvor 3206 manufactured by Sandoz, may be mentioned.

As a method for forming an ultraviolet blocking layer, a method may alsobe mentioned wherein a commercially available or preliminarily formedultraviolet blocking film, is bonded.

As the ultraviolet blocking film, a polyimide film or a film having anultraviolet absorber(s) coated or kneaded therein, may, for example, bementioned. For example, a commercially available ultraviolet blockingfilm such as UVGard manufactured by Fuji Photo Film Co., Ltd.;Scotchtint (TM) super layer SCLARL 150, SCLARL 400, SCLARL 600, ULTRA600, MUSHICLEAR Eco RE80CLIS, manufactured by 3M Co.; or Hallo Window-TKClear or BZA-50K, manufactured by Mitsubishi Polyester Film, LLC, may beused.

In a case where an ultraviolet blocking film is to be prepared, the filmmay be prepared, for example, by a known method by using a compositioncomprising the base resin, the ultraviolet absorber(s) and, ifnecessary, the oil-soluble dye(s) (the above-mentioned yellow dye(s)).Such a composition may be dissolved in a suitable solvent and then, bymeans of a known method using a bar coater or a die coater, the film maybe prepared by a known coating method.

Otherwise, the base resin, the ultraviolet absorber(s), the oil-solubledye(s), etc. may be mixed, and a resin may be kneaded under heating,followed by processing into a film by a known technique such asextrusion molding.

As the base resin, polymethyl methacrylate, polystyrene, polycarbonate,polyethylene, polypropylene or polyvinyl chloride may, for example, bementioned, but the base resin is not limited thereto. The content of theultraviolet absorber(s) is preferably from 1 to 30 wt %, based on thetotal solid content in the film-forming composition.

The oil-soluble dye(s) may suitably be selected from commerciallyavailable ones including the above-mentioned compounds as yellow dyes.The content of such a dye(s) is preferably from 0.01 to 20 wt %, basedon the total solid content in the film-forming composition.

The solvent may be any solvent so long as it is capable of dissolvingthe base resin, the ultraviolet absorber, the oil-soluble dye, etc. Forexample, an ether solvent such as tetrahydrofuran, an aromatic solventsuch as toluene, a ketone solvent such as methyl ethyl ketone or methylamyl ketone, or a propylene glycol solvent such as propylene glycolmonomethyl ether-2-acetate, may, for example, be mentioned.

The ultraviolet absorbers or the above yellow dyes may respectively beused in combination as a mixture of two or more of them. By using aplurality of them in combination, light rays in a wider range canefficiently be absorbed, such being preferred.

In the color dose meter of the present invention, as a means to preventdeterioration by ultraviolet rays, a method of forming an ultravioletblocking layer is more preferred.

In a case where the photochromic material of the present invention is acomposition represented by the above (2-1) to (2-3), as mentioned above,an ultraviolet absorber(s) may be incorporated in the composition. Assuch an ultraviolet absorber(s), the same compound(s) as the compound(s)disclosed above as one(s) to be incorporated to the ultraviolet blockinglayer, may be mentioned.

As described in (2-1), the color dose meter of the present invention maybe one having the solution or dispersion sealed in a cell, one havingthe resin composition described in (2-2) molded into a desired shape,one having the molded product described in (2-3) formed in a desiredshape, or a laminate of (2-4). Among them, from the viewpoint ofapplication to a medical means such as blood for transfusion, a tag-formor seal-form one employing it, is preferred.

Specifically, a method may be mentioned in which a cell or moldedproduct containing such a photochromic material, is bonded on part orthe entire surface of the film-form or plate-form substrate, and thesubstrate is formed into a tag and attached to a blood bag fortransfusion or to a medical equipment. A photochromic material may besandwiched between two substrates, and such an assembly may be formedinto a tag. Further, a method may be mentioned wherein the support layerof the laminate of (2-4) is formed in a tag shape and attached to ablood bag or a medical equipment in the same manner. The method forattaching is not particularly limited and may suitably be selecteddepending upon the shape of the blood bag or the medical equipment.

Likewise, as a seal-form color dose meter, a method may be mentionedwherein a laminate made of a photochromic material or a cell or moldedproduct containing a photochromic material, is bonded on part or theentire surface of a substrate, and an adhesive layer or a tackifierlayer is formed on the rear side, and then such an assembly is attachedto a blood bag for a medical equipment for use. Otherwise, aphotochromic material may be sandwiched between two substrates, and suchan assembly may be formed into a seal. Further, an adhesive layer or atackifier layer may be formed on the rear side of the support layeritself of the laminate of (2-4), and the product may be formed into aseal shape. The adhesive layer and the tackifier layer may be formed bycoating an adhesive layer or a tackifier, or a commercially availabledouble-stick tape or the like may be employed.

FIG. 4 shows an example of a seal-form color dose meter, and FIG. 5shows an example of a tag-form color dose meter. However, the tag-formor seal-form color dose meter of the present invention is not limited tothe above-described form or illustrated form.

In the foregoing, the present invention has been described in detailwith reference to specific embodiments, but it is apparent to thoseskilled in the art that with respect to the present invention, variouschanges or modifications may be made without departing from the gist andthe range of the present invention.

The present invention is based on Japanese Patent application No.2001-181418 filed on Jun. 15, 2001, and the entire disclosure is herebyincorporated to the present application by reference.

EXAMPLES

Now, the present invention will be described in further detail withreference to Examples, but it should be understood that the presentinvention is by no means restricted to such specific Examples.

Example 1

0.02 g of the above diarylethene compound (1) (a photochromic compound;quantum yield in the ring opening reaction: 1.3×10⁻²) and 0.2 g of apolystyrene resin were dissolved in 0.51 g of toluene, and 0.1 g ofCeMgAl₁₁O₁₉ was added as an ultraviolet-emitting phosphor (illuminant),followed by stirring. Then, a white film having a thickness of 0.5 mmwas prepared by a casting method.

To the prepared film, 100 Gy of γ-rays were irradiated by using ⁶⁰Co asa radiation source, whereby the absorption spectra in the visible lightwavelength range before and after the irradiation were measured. For themeasurement, “Shimadzu Automatic Spectrophotometer UV-3100PC”(manufactured by Shimadzu Corporation) was employed, and the absorbanceat 600 nm as the maximum absorption wavelength of the compound (1), wasmeasured. The results are shown in Table 1.

Example 2

The test was carried out under the same conditions as in Example 1except that the ultraviolet-emitting phosphor (illuminant) CeMgAl₁₁O₁₉in Example 1 was changed to SrB₄O₇:Eu²⁺. The results are shown in Table1 given hereinafter.

Example 3

4 g of an ultraviolet-emitting phosphor (illuminant) CeMgAl₁₁O₁₉ and 0.5g of polyvinyl butyral were added to 5 ml of ethanol, followed bystirring. Then, coating and film-forming were carried out by means of abar coater method on a support having an aluminum foil as a reflectionplate provided on a transparent polyethylene terephthalate, to form aluminescent layer having a thickness of 0.1 mm. Further, a solutionhaving 0.2 g of a polystyrene resin and 0.02 g of the above compound (1)(a photochromic compound) dissolved in toluene, was cast thereon, toform a photochromic layer having a thickness of 0.3 mm. To the preparedfilm, 100 Gy of γ-rays were irradiated by using ⁶⁰Co as a radiationsource, whereby the absorption spectra in the visible light range of thephotochromic layer before and after the irradiation, were measured. Thechange in the absorbance at a wavelength of 600 nm as between before andafter the irradiation of γ-rays, is shown in Table 1 given hereinafter.

Comparative Example 1

A film was prepared under the same conditions as in Example 1 exceptthat the ultraviolet-emitting phosphor (illuminant) CeMgAl₁₁O₁₉ inExample 1 was omitted, and the same test as in Example 1 was carriedout. The results are shown in Table 1.

Comparative Example 2

A film was prepared under the same conditions as in Example 1 exceptthat the ultraviolet-emitting phosphor (illuminant) CeMgAl₁₁O₁₉ inExample 1 was changed to HfO₂, and the same test as in Example 1 wascarried out. The results are shown in Table 1.

Comparative Example 3

A film was prepared under the same conditions as in Example 1 exceptthat the ultraviolet-emitting phosphor (illuminant) CeMgAl₁₁O₁₉ inExample 1 was changed to Bi₂O₃, and the same test as in Example 1 wascarried out. The results are shown in Table 1.

Comparative Example 4

A film was prepared under the same conditions as in Example 3 exceptthat the luminescent layer containing the ultraviolet-emitting phosphor(illuminant) CeMgAl₁₁O₁₉ in Example 3 was omitted, and the same test asin Example 1 was carried out. The results are shown in Table 1.

Examples 4 to 6

Films were prepared by a casting method in the same manner as in Example1 except that CeMgAl₁₁O₁₉ was changed to the respective phosphors shownin Table 1. With respect to these films, the change in absorbance at awavelength of 600 nm as between before and after the irradiation ofγ-rays was measured in the same manner as in Example 1, and the resultsare shown in Table 1.

TABLE 1 Relative Change in value of the Thickness of absorbance changein Illuminant the layer at a absorbance Photo- (emission Irradiated Formof containing wavelength to (a) in chromic wavelength/ lightphotochromic photochromic of 600 nm: Comparative compound nm)(intensity) material compound (mm) (a) Example 1*1 Example 1 CompoundCeMgAl₁₁O₁₉ γ-rays (⁶⁰Co) (2-2) resin 0.5 0.15 6 (1) (350 nm) (100Gy)composition Example 2 Compound SrB₄O₇:Eu²⁺ γ-rays(⁶⁰Co) (2-2) resin 0.50.036 1.4 (1) (369 nm) (100Gy) composition Example 3 CompoundCeMgAl₁₁O₁₉ γ-rays(⁶⁰Co) (2-4) laminate 0.5 0.07 2.8^(*1) (1) (350 nm)(100Gy) Example 4 Compound ZnS:Ag γ-rays(⁶⁰Co) (2-2) resin 0.5 0.11 4.4(1) (450 nm) (100Gy) composition Example 5 Compound CaWO₄ γ-rays(⁶⁰Co)(2-2) resin 0.5 0.097 3.9 (1) (425 nm) (100Gy) composition Example 6Compound BaFCl:Eu²⁺ γ-rays(⁶⁰Co) (2-2) resin 0.5 0.11 4.4 (1) (385 nm)(100Gy) composition Comparative Compound Nil γ-rays(⁶⁰Co) (2-2) resin0.5 0.025 1 Example 1 (1) (100Gy) composition Comparative Compound HfO₂γ-rays(⁶⁰Co) (2-2) resin 0.5 0.008 0.32 Example 2 (1) (No (100Gy)composition emission) Comparative Compound Bi₂O₃ γ-rays(⁶⁰Co) (2-2)resin 0.5 0.0019 0.08 Example 3 (1) (No (100Gy) composition emission)Comparative Compound Nil γ-rays(⁶⁰Co) (2-4) laminate 0.5 0.025 1 Example4 (1) (100Gy) *1: Only in Example 3, the relative value is toComparative Example 4.

In Table 1, it is considered that the larger the relative value of thechange in absorbance (light-most column), the higher the sensitivity indetecting the radiation (γ-rays). The relative values of the change inabsorbance of the films containing the photochromic materials of thepresent invention (Examples 1 to 6) are larger than the relative valuesof the change in absorbance of the films not containing the photochromicmaterial of the present invention (Comparative Examples 1 to 4), wherebyit is evident that the films containing the photochromic materials ofthe present invention have higher sensitivities in detecting theradiation.

Then, the change in absorbance of samples by irradiation of X-rays wasinvestigated.

Example 7

To the sample prepared in Example 1, 45 Gy of X-rays were irradiated bymeans of a soft X-ray irradiation apparatus “SOFTEX M-80W special model”(50 kV, 4 mA), manufactured by Softex K.K.), whereby the sampleunderwent a color change to blue. With respect to the absorption spectraof the sample before and after the irradiation, the change in absorbanceat a wavelength of 600 nm was measured. The results are shown in Table2.

Example 8

A sample was prepared in the same manner as in Example 1 except that thephosphor was changed from CeMgAl₁₁O₁₉ to BaFCl:Eu²⁺, and X-rays wereirradiated in the same manner as in Example 7, whereby the sampleunderwent a color change to blue. With respect to the absorption spectraof the sample before and after the irradiation, the change in absorbanceat a wavelength of 600 nm was measured. The results are shown in Table2. Further, this sample underwent no color change also in a case where100 Gy of X-rays were irradiated.

Comparative Example 5

A sample was prepared in the same manner as in Example 7 except that thediarylethene compound was changed to the following compound (2):

and X-rays were irradiated in the same manner as in Example 7, wherebythe sample underwent no color change. With respect to the absorptionspectra of the sample before and after the irradiation, the change inabsorbance at a wavelength of 600 nm was measured. The results are shownin Table 2. Further, with the sample employing the above compound (2),no change in absorbance was observed also in a case where 100 Gy ofX-rays were irradiated.

Comparative Example 6

To the sample prepared in Comparative Example 1, X-rays were irradiatedin the same manner as in Example 7. With respect to the absorptionspectra of the sample before and after the irradiation, the change inabsorbance at a wavelength of 600 nm was measured. The results are shownin Table 2.

TABLE 2 Relative value of Change in the change Thickness of absorbancein Illuminant the layer at a absorbance Photo- (emission Irradiated Formof containing wavelength to (a) in chromic wavelength/ lightphotochromic photochromic of 600 nm: Comparative compound nm)(intensity) material compound (mm) (a) Example 6 Example 7 CompoundCeMgAl₁₁O₁₉ X-rays (2-2) resin 0.5 0.17 7 (1) (350 nm) (45Gy)composition Example 8 Compound BaFCl:Eu²⁺ X-rays (2-2) resin 0.5 0.114.8 (1) (385 nm) (45Gy) composition Comparative Compound CeMgAl₁₁O₁₉X-rays (2-2) resin 0.5 0 0 Example 5 (2) (350 nm) (45Gy) compositionComparative Compound Nil X-rays (2-2) resin 0.5 0.023 1 Example 6 (1)(45Gy) composition

As shown in Table 2, in a case where the diarylethene compoundrepresented by the formula (I) is not used, no color change was observedby the X-ray irradiation with an intensity at a level which is commonlyused for blood for transfusion.

Example 9

0.02 g of the above diarylethene compound (3) (photochromic compound;quantum yield in the ring-opening reaction: 1.7×10⁻⁵) and 0.2 g of apolystyrene resin were dissolved in 0.51 g of toluene, and 0.1 g ofBaFCl:Eu²⁺ was added as an ultraviolet-emitting phosphor (illuminant),followed by stirring. Then, a white film having a thickness of 0.3 mmwas prepared by a casting method.

To the prepared film, 15 Gy of X-rays were irradiated by means of thesame X-ray apparatus as in Example 7, whereby the reflection spectra inthe visible light wavelength range before and after the irradiation weremeasured. For the measurement, an integrating sphere apparatus“ISR-3100” (manufactured by Shimadzu Corporation) was employed, and thereflectance at 645 nm as the maximum absorption wavelength of thecompound (3), was measured. The results are shown in Table 3.

Comparative Example 7

A white film was prepared in the same manner as in Example 9 except thatthe phosphor BaFCl:Eu²⁺ was not used, and the change in reflectance at awavelength of 645 nm was measured. The results are shown in Table 3.

TABLE 3 Relative value of Thickness of Change in the change the layerreflectance in Illuminant containing at a reflectance Photo- (emissionIrradiated Form of photochromic wavelength to (b) in chromic wavelength/light photochromic compound of 645 Comparative compound nm) (intensity)material (mm) nm: (b) Example 7 Example 9 Compound BaFCl:Eu²⁺ X-rays(2-2) resin 0.3 0.51 7 (3) (385 nm) (45Gy) composition ComparativeCompound Nil X-rays (2-2) resin 0.3 0.07 4.8 Example 7 (3) (45Gy)composition

INDUSTRIAL APPLICABILITY

According to the photochromic material of the present invention and acolor dose meter employing it, a diarylethene compound which shifts to acolor-changed isomer when irradiated with a light in a specificwavelength band, is used in combination with an illuminant which emits alight having a wavelength band which overlaps the above-mentionedwavelength band upon absorption of a radiation, whereby the irradiatedradiation can efficiently be detected, and it will be possible tomeasure the dose with high sensitivity.

The invention claimed is:
 1. A photochromic material, comprising: one ormore illuminants which emits a light when irradiated with radiation, oneor more diarylethene compounds, wherein the diarylethene compound isrepresented by the following formula (0), and the absorption spectrum ofthe ring opened form of the diarylethene compound, and the emissionspectrum of the illuminant, overlap each other:

wherein formula (0), each of the groups R¹ and R² which are independentof each other, is an alkyl group, a cycloalkyl group or an alkoxy group,each of groups X¹, X², Y¹ and Y² which are independent of one another,is one of

the group R³ is a hydrogen atom, an alkyl group which may besubstituted, an aryl group which may be substituted, or a cycloalkylgroup which may be substituted, the group R⁴ is a hydrogen atom, analkyl group which may be substituted, or a cycloalkyl group which may besubstituted, the ring D¹ is a 5- or 6-membered aromatic ring which isformed by groups X¹ and Y¹ together with two carbon atoms bonded theretoand which may be substituted, and the ring E¹ is a 5- or 6-memberedaromatic ring which is formed by groups X² and Y² together with twocarbon atoms bonded thereto and which may be substituted, the rings D¹and E¹ may further have a 5- or 6-membered aromatic ring which may besubstituted, condensed thereto; and one or more ultraviolet absorbers.2. The photochromic material according to claim 1, wherein thediarylethene compound is represented by formula (I):

wherein formula (I), each of the groups R¹¹ and R¹² which areindependent of each other, is an alkyl group, a cycloalkyl group or analkoxy group, each of the groups X¹¹ and X¹² which are independent ofeach other, is one of

each of groups Y¹¹ and Y¹² which are independent of each other, is oneof

each of the groups R¹⁵ and R¹⁶ are in dependent of each other, is ahydrogen atom, an alkyl group which may be substituted, an aryl groupwhich may be substituted, a heteroaryl group which may be substituted,or a cycloalkyl group which may be substituted, when at least one ofgroup Y¹¹ or group Y¹² is

at least one of group R¹⁵ or group R¹⁶ may be bonded to group R¹⁷ toform a 5- or 6-membered aromatic ring which may have a substituent, thegroup R¹³ is a hydrogen atom, an alkyl group which may be substituted,an aryl group which may be substituted, or a cycloalkyl group which maybe substituted, the group R¹⁷ is a hydrogen atom, an alkyl group whichmay be substituted, or a cycloalkyl group which may be substituted. 3.The photochromic material according to claim 1, wherein the diarylethenecompound is represented by formula (II)

wherein formula (II), each of the groups R²¹ and R²² which areindependent of each other, is an alkyl group, a cycloalkyl group or analkoxy group, each of the groups X²¹ and X²² which are independent ofeach other, is one of

each of the groups Y²¹ and Y²² which are independent of each other, isone of

each of the groups R²⁵ and R²⁶ which are independent of each other, is ahydrogen atom, an alkyl group which may be substituted, an aryl groupwhich may be substituted, a heteroaryl group which may be substituted,or a cycloalkyl group which may be substituted, when at least one ofgroup Y²¹ or group Y²² is

at least one of group R²⁵ or group may be bonded to group R²⁷ to form a5- or 6-membered aromatic ring, the group R²³ is a hydrogen atom, analkyl group which may be substituted, an aryl group which may besubstituted, or a cycloalkyl group which may be substituted, the groupR²⁷ is a hydrogen atom, an alkyl group which may be substituted, or acycloalkyl group which may be substituted.
 4. The photochromic materialaccording to claim 1, wherein the diarylethene compound is heatirreversible.
 5. The photochromic material according to claim 1, whereinthe quantum yield in the ring opening reaction of the diarylethenecompound is at most 10⁻³.
 6. The photochromic material according toclaim 1, wherein the illuminant is an ultraviolet ray emitting phosphor.7. The photochromic material according to claim 1, which is acomposition comprising said one or more illuminants, diarylethenecompounds and ultraviolet absorbers.
 8. The photochromic materialaccording to claim 1, wherein a layer of said one or more ultravioletabsorbers is formed on said one or more illuminants and said one or morediarylethene compounds.
 9. A color dose meter which comprises thephotochromic material as defined in claim 1.